1. Field of the Invention
The present invention relates to phosphorus-containing polymers useful in fiber or resin manufacture. More preferably, the present invention is directed to polyamide polymers having phosphinic acid-salt groups in the polymer chain and which exhibit stain and flame resistance.
The term "fiber" as used herein is defined to include fibers of extreme or indefinite length (i.e., filaments) as well as fibers of short length (i.e., staple).
The term "yarn" as used herein is defined to be a continuous strand of fibers.
The term "polyamide" as used herein is defined to be a polymer whose repeating units are joined by amide linkages.
The term "polymer" as used herein is defined to encompass homopolymers, copolymers and the like, as well as polymer blends.
The term "resin" as used herein includes (but is not limited to) plastics used in molded or extruded parts.
2. Background of the Invention
Carpet with pile made from polyamide fibers has become a popular floor covering for both residential and commercial applications. Such carpet is relatively inexpensive and offers a desirable combination of qualities including durability, comfort, safety, warmth and aesthetic appearance. Polyamide fibers, for example fibers of polyhexamethylene adipamide (more commonly known as nylon 6,6) or polycaprolactam (more commonly known as nylon 6) are of specific value in this utility.
In many polyamide pile carpet manufacturing processes, the pile is dyed to a desired color with acid dyes, as many polyamides including nylon 6,6 and nylon 6 are very receptive to these dyes. This receptivity to acid dyes, however, can also manifest itself in a susceptibility to staining by natural or artificial acid dyes which typically exist in numerous consumer products such as foods and drinks.
One known method to impart stain resistance to nylon fibers includes topically applying to the fiber surface certain materials or compounds which function as stainblockers, such as those disclosed in U.S. Pat. No. 4,879,180 to Blyth et al. While this topical treatment successfully improves resistance to staining by acid dyes, the degree of stain resistance can decrease over time if the carpet is subjected to heavy use or harsh chemical cleaning.
Alternatively, it is known from, for example, U.S. Pat. No. 4,579,762 to Ucci, to form stain resistant fibers from nylon 6 or 6,6 polymer having a portion of the nylon-forming monomers replaced with a corresponding amount of an appropriate sulfonated aromatic monomer. Unfortunately, these polymers can exhibit undesirable foaming during polymerization.
Phosphorus-containing polyamides, as well as fibers and films formed therefrom, have been reported in the prior art. For example, U.S. Pat. No. 2,646,420 discloses high shrinkage fibers of polyamides containing recurring ##STR3## radicals joined by amide linkages while British Patent No. 1,102,009 discloses low melting polyamide films containing recurring ##STR4## Also, U.S. Pat. No. 3,108,991 discloses water soluble, flame resistant homopolyamides containing, for example, recurring ##STR5## units, where R is a lower alkyl. Phosphorus-containing polyamides useful in certain applications are also disclosed in U.S. Pat. No. 4,092,302, assigned to the assignee of the present invention.
None of these phosphorus-containing polyamides are shown to exhibit any degree of resistance to staining by acid dyes.
A need therefore exists for a polymer which provides the beneficial characteristics of polyamides without the acid dye stain susceptibility that many polyamides exhibit.